According to this :2011-'12 Chevrolet Cruze Recalled for Brake-Assist Defect | Edmunds.com it is a cold start issue "He said the problem sometimes becomes apparent during a "cold start."I've seen it happen...although I'm wondering if it has more to do with the valve timing/overlap when warming up in these engines? I know that's why they started using vacuum assist pumps in other VVT motors, and it let them get rid of EGR valves. Or maybe just the 1500 RPM idle when cold.
Color me curious.